A hybrid automatic repeat request (HARQ) operation can be applied as a method for controlling data reception failure. When a data transmitter receives an ACK signal from a data receiver after transmitting a packet to the data receiver, the data transmitter can transmit a new packet. If the data transmitter receives a NACK signal from the data receiver, the data transmitter can retransmit the previously transmitted packet. In this case, a packet to which encoding according to forward error correction (FEC) has been applied can be retransmitted. Accordingly, the data receiver decodes a received packet and transmits an ACK signal upon successfully decoding the received packet. When the data receiver does not successfully decode the received packet, the data receiver transmits a NACK signal and stores the received packet in a buffer. Upon reception of a retransmitted packet according to the NACK signal, the data receiver combines the retransmitted packet with the packet stored in the buffer and decodes the combined packet to improve packet reception success rate.
In accordance with a synchronous HARQ operation of the conventional wireless communication system, 8 independent HARQ processes are defined. In addition, one HARQ process is associated with one transmission (Tx) time, and each HARQ process is defined to have a time period of 8 msec. For example, assuming that initial transmission of UL data is performed at a subframe n through a HARQ process #1, if the corresponding UL data is retransmitted at a subframe n+8, retransmission of the UL Data is performed at the same HARQ process #1.